There have been developed a number of different surgical techniques to correct hyperopic or myopic conditions of a human eye. U.S. Pat. No. 4,840,175 issued to Peyman discloses a procedure wherein a thin layer of a cornea is cut to expose the stroma layer of the cornea. A laser beam is then directed onto the exposed corneal tissue in a predetermined pattern. The laser beam ablates corneal tissue and changes the curvature of the eye. This procedure is sometimes referred to as Laser in situ Keratomileusis (LASIK).
U.S. Pat. No. Re 35,421 issued to Ruiz et al. discloses a device for cutting a cornea in a LASIK procedure. Such a device is commonly referred to as a microkeratome. The Ruiz microkeratome includes a ring that is placed onto a cornea and a blade that is located within an opening of the ring. The device also contains a drive mechanism which moves the blade across the cornea in a first direction while the blade moves in a reciprocating transverse direction to cut the eye. The device can create a lamella flap of the cornea which is flipped back so that the stromal bed of the cornea can be ablated with a laser.
U.S. Pat. No. 6,051,009 issued to Hellenkamp et al. discloses a microkeratome that is sold under the trademark HANSATOME. The HANSATOME microkeratome moves the blade in an arcuate path about the cornea. The HANSATOME microkeratome includes a disposable blade assembly that can be loaded and removed from the device. The blade assembly includes a blade holder that is attached to a cutting blade. The blade holder has a recess that receives the end of a drive shaft. Rotation of the output shaft moves the blade in an arcuate path, and moves the blade in a back-and-forth motion to create the lamella flap of the cornea.
Microkeratomes have three primary components, a hand piece that contains a motor, a head that holds the blade, and a ring that applies a suction to maintain the position of the microkeratome relative to the cornea. Because the microkeratome is in contact with patient tissue it must be cleaned after each procedure, typically involving an autoclave. The head has a number of small cavities that are more difficult to clean. Additionally, the autoclave process may degrade the head after a number of procedures and cleaning cycles. It would be desirable to provide a microkeratome that does not require the head to be sterilized after each surgical procedure.
The blades used to cut tissue are replaced after each procedure. The replacement blades are typically loaded into the head of the microkeratome with a pair of forceps. The blade must be loaded accurately so that a drive pin of the motor assembly is inserted into a corresponding slot of a blade holder. Accurately loading the blade with forceps can be a time consuming process. It would be desirable to provide a blade package that can be used to accurately load a blade into a microkeratome in a time efficient manner.
A complication may occur while the microkeratome is cutting the lamella flap. It may be desirable to remove the microkeratome in the middle of a cut. Removing the microkeratome requires releasing the vacuum of the suction ring. Releasing the vacuum allows the cornea to move back to its original shape. Movement of the cornea will also cause the blade to move. Movement of the blade may cause damage to the cornea. It would be desirable to provide a microkeratome that allows a surgeon to remove the head while the suction ring is still fixed to the cornea. It would also be desirable to provide a microkeratome that allows the surgeon to vary the thickness of the lamella flap hinge.
Another problem attending the use of microkeratome cutting heads of known designs is the occurrence of a buttonhole (or dimple) in the cornea, which is a result of the cutting procedure. A buttonhole generally is a depression in the central region of the cornea, which results in an uncut island of tissue and is created as a conventionally designed cutting head passes over the cornea. The buttonhole is highly undesirable as it results in the blade cutting only the peripheral tissue that is at a higher elevation than the tissue in the central cornea where the buttonhole exists. Thus, a flap having a hole at its center is thereby created instead of an intended continuous or unbroken corneal flap. The occurrence of the buttonhole and consequent peripheral cutting event typically require that the surgeon lay the corneal flap (having the hole in its center) back down on the stromal bed of the cornea and wait a few months to attempt the intended procedure again. Therefore, there is also a need for providing a microkeratome that prevents the occurrence of such buttonholes, dimples, or depressions in the corneal tissue.
The microkeratome is commonly used in conjunction with an artificial anterior chamber (AAC) were the donor eye is situated, and creates a fixture from which the microkeratome can retrieve a graft. Examples of an artificial anterior chamber include U.S. Pat. No. 6,045,563 to Duprat; U.S. Patent Application Publication No. US2008/0249548 to Weston; and U.S. Patent Application Publication No. US2008/0269769 to Dybbs.